U.S. patent application number 12/466514 was filed with the patent office on 2010-11-18 for power distribution devices, systems, and methods for radio-over-fiber (rof) distributed communication.
Invention is credited to Terry D. Cox.
Application Number | 20100290787 12/466514 |
Document ID | / |
Family ID | 42342709 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100290787 |
Kind Code |
A1 |
Cox; Terry D. |
November 18, 2010 |
Power Distribution Devices, Systems, and Methods for
Radio-Over-Fiber (RoF) Distributed Communication
Abstract
Power distribution devices, systems and methods for a
Radio-over-Fiber (RoF) distributed communication system are
disclosed. In one embodiment, an interconnect unit is coupled
between a head-end unit and one or more remote units. The
interconnect unit includes a plurality of optical communication
links each configured to carry RoF signals to and from a head-end
unit to remote units. The RF electrical signals from the head-end
unit are converted to RF optical signals and communicated over the
optical communication links in the interconnect unit to the remote
units. The remote units convert the optical signals to electrical
signals and communicate the electrical signals to client devices.
To provide power to the remote units, the interconnect unit
electrically couples power from at least one power supply to a
plurality of power branches. Each power branch is configured to
supply power to a remote unit connected to the interconnect
unit.
Inventors: |
Cox; Terry D.; (Keller,
TX) |
Correspondence
Address: |
CORNING INCORPORATED
INTELLECTUAL PROPERTY DEPARTMENT, SP-TI-3-1
CORNING
NY
14831
US
|
Family ID: |
42342709 |
Appl. No.: |
12/466514 |
Filed: |
May 15, 2009 |
Current U.S.
Class: |
398/115 |
Current CPC
Class: |
H04B 10/25753 20130101;
H04B 10/808 20130101 |
Class at
Publication: |
398/115 |
International
Class: |
H04B 10/00 20060101
H04B010/00 |
Claims
1. An interconnect unit for a Radio-over-Fiber (RoF) wireless
communication system, comprising: a plurality of optical
communication links each configured to carry an RoF signal from a
head-end unit to a plurality of remote units; and at least one
power supply electrically coupled to a plurality of power branches
each configured to supply power to a remote unit among the
plurality of remote units.
2. The interconnect unit of claim 1, wherein each of the plurality
of optical communication links comprises: an optical communication
input link configured to receive the RoF signal from the head-end
unit; and an optical communication output link optically connected
to the optical communication input link and configured to provide
an optical connection between the head-end unit and the plurality
of remote units.
3. The interconnect unit of claim 1, further comprising a power
distribution module electrically coupled between the at least one
power supply and the plurality of power branches and configured to
distribute power to the plurality of remote units.
4. The interconnect unit of claim 3, wherein the power distribution
module comprises a voltage protection circuit.
5. The interconnect unit of claim 4, wherein the voltage protection
circuit comprises an over-voltage protection circuit.
6. The interconnect unit of claim 5, wherein the voltage protection
circuit further comprises a reverse-voltage protection circuit.
7. The interconnect unit of claim 4, wherein the voltage protection
circuit comprises a reverse-voltage protection circuit.
8. The interconnect unit of claim 4, wherein the voltage protection
circuit is coupled to a common branch in the power distribution
module coupled to the plurality of power branches.
9. The interconnect unit of claim 3, wherein the power distribution
module comprises a current protection circuit.
10. The interconnect unit of claim 9, wherein the power
distribution module further comprises a voltage protection
circuit.
11. The interconnect unit of claim 9, wherein the current
protection circuit is comprised of an over-current protection
circuit.
12. The interconnect unit of claim 9, wherein the current
protection circuit is comprised of a plurality of current
protection circuits each coupled to a power branch among the
plurality of power branches.
13. The interconnect unit of claim 3, wherein the power
distribution module comprises an under-voltage sensing circuit.
14. The interconnect unit of claim 13, wherein the under-voltage
sensing circuit is comprised of a plurality of under-voltage
sensing circuits each coupled to a power branch among the plurality
of power branches.
15. The interconnect unit of claim 14, further comprising a power
indicator coupled to the under-voltage sensing circuit and
configured to generate a visual indicator when the under-voltage
sensing circuit senses an under-voltage.
16. The interconnect unit of claim 1, wherein the at least one
power supply comprises at least one Safety Extra Low Voltage (SELV)
power supply.
17. The interconnect unit of claim 1, wherein the at least one
power supply is comprised a plurality of power supplies each
configured to supply power to a different set of remote units among
the plurality of remote units.
18. A method of distributing power to a plurality of remote units
in a Radio-over-Fiber (RoF) communication system, comprising:
receiving RoF signals over a plurality of optical communication
links in an interconnect unit from a head-end unit; providing power
from at least one power supply in the interconnect unit to a
plurality of power branches; distributing the RoF signals from each
of the plurality of optical communication links to a remote unit
among a plurality of remote units; and distributing power from each
of the plurality of power branches to a remote unit among the
plurality of remote units.
19. The method of claim 18, further comprising protecting the
plurality of power branches from an over-voltage condition from the
at least one power supply.
20. The method of claim 18, further comprising protecting the
plurality of power branches from a reverse-voltage condition from
the at least one power supply.
21. The method of claim 18, further comprising protecting the
plurality of power branches from an over-current condition from the
at least one power supply.
22. The method of claim 18, further comprising sensing an
under-voltage condition in each power branch among the plurality of
power branches.
23. A Radio-over-Fiber (RoF) wireless communication system,
comprising: at least one interconnect unit, comprising: a plurality
of optical communication links each configured to carry an RoF
signal from a head-end unit; and at least one power supply
electrically coupled to a plurality of power branches; and a
plurality of remote units each comprising: a power input port
electrically coupled to one of the plurality of power branches; and
an optical communication input port optically connected to one of
the plurality of optical communication links to receive the RoF
signal from the head-end unit.
24. The RoF wireless communication system of claim 23, further
comprising a power distribution module electrically coupled between
the at least one power supply and the plurality of power branches
and configured to distribute power to the plurality of remote
units.
25. The RoF wireless communication system of claim 24, wherein the
power distribution module comprises either a voltage protection
circuit, a current protection circuit, or both a voltage protection
circuit and a current protection circuit.
26. The RoF wireless communication system of claim 23, wherein the
at least one interconnect unit is comprised of a plurality of
interconnect units.
27. The RoF wireless communication system of claim 23, wherein the
at least one power supply is comprised of a plurality of power
supplies each configured to supply power to a different set of
remote units among the plurality of remote units.
28. The RoF wireless communication system of claim 23, wherein each
of the plurality of remote units comprises an optical-to-electrical
(O-E) converter and an electrical-to-optical (E-O) converter each
electrically coupled to the power input port.
29. The RoF wireless communication system of claim 23, wherein: the
power input port is electrically coupled to one of the plurality of
power branches via a fiber optic cable comprising electrical
conductors; and the optical communication input port is optically
connected to one of the plurality of optical communication links
via a downlink optical fiber and an uplink optical fiber provided
in the fiber optic cable.
Description
TECHNICAL FIELD
[0001] The technology of the disclosure relates to providing power
to remote units in a Radio-over-Fiber (RoF) distributed
communication system.
BACKGROUND
[0002] Wireless communication is rapidly growing, with
ever-increasing demands for high-speed mobile data communication.
As an example, so-called "wireless fidelity" or "WiFi" systems and
wireless local area networks (WLANs) are being deployed in many
different types of areas (e.g., coffee shops, airports, libraries,
etc.). Wireless communication systems communicate with wireless
devices called "clients," which must reside within the wireless
range or "cell coverage area" in order to communicate with an
access point device.
[0003] One approach to deploying a wireless communication system
involves the use of "picocells." Picocells are radio-frequency (RF)
coverage areas. Picocells can have a radius in the range from a few
meters up to twenty meters as an example. Combining a number of
access point devices creates an array of picocells that cover an
area called a "picocellular coverage area." Because the picocell
covers a small area, there are typically only a few users (clients)
per picocell. This reduces the amount of RF bandwidth shared among
the wireless system users.
[0004] "Radio-over-Fiber" (RoF) wireless systems can be used to
create picocells. A RoF wireless system utilizes RF signals
conveyed over optical fibers. Such systems include a head-end
station optically coupled to a plurality of remote units. The
remote units each include transponders that are coupled to the
head-end station via an optical fiber link. The transponders in the
remote units are transparent to the RF signals. The remote units
simply convert incoming optical signals from the optical fiber link
to electrical signals via optical-to-electrical (O/E) converters,
which are then passed to the transponders. The transponders convert
the electrical signals to electromagnetic signals via antennas
coupled to the transponders in the remote units. The antennas also
receive electromagnetic signals from clients in the cell coverage
area and convert the electromagnetic signals to electrical signals.
The remote units then convert the electrical signals to optical
signals via electrical-to-optical (E/O) converters. The optical
signals are then sent to the head-end station via the optical fiber
link. Because the remote units include power consuming components,
including O/E and E/O converters, electrical power must be provided
to the remote units.
SUMMARY
[0005] Embodiments disclosed in the detailed description include
power distribution devices, systems, and methods for
Radio-over-Fiber (RoF) distributed communications. In one
embodiment, an interconnect unit is coupled between a head-end unit
and one or more remote units. The interconnect unit includes a
plurality of optical communication links each configured to carry
RoF signals between a head-end unit and a remote unit. To provide
power to the remote units, the interconnect unit electrically
couples power from at least one power supply to a plurality of
power branches in the interconnect unit. Each power branch is
configured to supply power to a remote unit when connected to the
interconnect unit. In this manner, power is not required to be run
from the heat-end unit to the remote units. Further, power supplies
are not required in the remote units, would require additional
space and also require each remote unit to be located in proximity
to a power source, thus decreasing flexibility in placement in a
building or other area.
[0006] In one embodiment, the electrical signals from the head-end
unit are converted to optical signals and communicated over the
optical communication links to the remote units via optical
connections established in the interconnect unit. The remote units
convert the optical signals to electrical signals and radiate the
electrical signals via an antenna to client devices in the range of
the antenna to provide a picocell. Each picocell from the remote
units can be combined to form a picocell coverage area or areas for
client device communications.
[0007] In another embodiment, the interconnect unit includes a bulk
power supply that is configured to supply power to all remote units
connected to the interconnect unit. In another embodiment, a
plurality of power supplies are provided wherein power is
partitioned from each power supply to a subset of remote units
connected to the interconnect unit.
[0008] In another embodiment, a power distribution module is also
provided in the interconnect unit to facilitate distribution of
power to remote units connected to the interconnect unit. The power
distribution module can be electrically coupled between a power
supply and a plurality of power branches and configured to
distribute power to a plurality of remote units. The power
distribution module can provide one or more protection circuits to
protect the interconnect unit and the remote units from damage
caused by power irregularities or related power conditions,
including power surges and electrostatic discharge (ESD) events as
examples. In one embodiment, the power distribution module includes
a voltage protection circuit. The voltage protection circuit may
include an over-voltage protection circuit and/or a reverse-voltage
protection circuit. In another embodiment, the power distribution
module can include a current protection circuit. The current
protection circuit can include an over-current protection circuit.
An under-voltage sensing circuit and power level indicators may
also be provided to indicate when the power level is not sufficient
to properly operate the remote units.
[0009] Additional features and advantages will be set forth in the
detailed description which follows, and in part will be readily
apparent to those skilled in the art from that description or
recognized by practicing the embodiments as described herein,
including the detailed description that follows, the claims, as
well as the appended drawings.
[0010] It is to be understood that both the foregoing general
description and the following detailed description present
embodiments, and are intended to provide an overview or framework
for understanding the nature and character of the disclosure. The
accompanying drawings are included to provide a further
understanding, and are incorporated into and constitute a part of
this specification. The drawings illustrate various embodiments,
and together with the description serve to explain the principles
and operation of the concepts disclosed.
BRIEF DESCRIPTION OF THE FIGURES
[0011] FIG. 1 is a schematic diagram of an exemplary
Radio-over-Fiber (RoF) distributed communication system;
[0012] FIG. 2 is a schematic diagram of the head-end unit (HEU),
interconnect unit (ICU), and one remote unit and picocell of the
exemplary Radio-over-Fiber (RoF) distributed communication system
of FIG. 1;
[0013] FIG. 3 is a schematic diagram of the exemplary ICU and power
distribution module of FIGS. 1 and 2;
[0014] FIG. 4 is a schematic diagram of an exemplary voltage
protection circuit of the power distribution module of FIG. 3;
[0015] FIG. 5 is a schematic diagram of an exemplary current
protection circuit and an exemplary under-voltage sensing modules
of the power distribution module of FIG. 3;
[0016] FIG. 6 is a schematic diagram of an alternative exemplary
ICU and power distribution modules that can be employed in the
exemplary Radio-over-Fiber (RoF) distributed communication system
of FIGS. 1 and 2; and
[0017] FIG. 7 illustrates an exemplary interconnect unit (ICU) that
may be employed in the exemplary Radio-over-Fiber (RoF) distributed
communication system of FIGS. 1 and 2.
DETAILED DESCRIPTION
[0018] Reference will now be made in detail to the embodiments,
examples of which are illustrated in the accompanying drawings, in
which some, but not all embodiments are shown. Indeed, the concepts
may be embodied in many different forms and should not be construed
as limiting herein; rather, these embodiments are provided so that
this disclosure will satisfy applicable legal requirements.
Whenever possible, like reference numbers will be used to refer to
like components or parts.
[0019] Embodiments disclosed in the detailed description include
power distribution devices, systems, and methods for
Radio-over-Fiber (RoF) distributed communications. In one
embodiment, an interconnect unit is coupled between a head-end unit
and one or more remote units. The interconnect unit includes a
plurality of optical communication links each configured to carry
RoF signals between a head-end unit and a remote unit. To provide
power to the remote units, the interconnect unit electrically
couples power from one or more power supplies to a plurality of
power branches in the interconnect unit. Each power branch is
configured to supply power to a remote unit when connected to the
interconnect unit. In this manner, power is not required to be run
from the head-end unit to the remote units. Further, power supplies
are not required in the remote units, would require additional
space and also require each remote unit to be located in proximity
to a power source, thus decreasing flexibility in placement in a
building or other area.
[0020] Although the embodiments of power distribution from
interconnect units (ICUs) to remote units described herein can be
used and employed in any type of RoF distributed communication
system, an exemplary RoF distributed communication system 10 is
provided in FIG. 1 to facilitate discussion of power distribution.
FIG. 1 includes a partially schematic cut-away diagram of a
building infrastructure 12 that generally represents any type of
building in which the RoF distributed communication system 10 might
be employed and used. The building infrastructure 12 includes a
first (ground) floor 14, a second floor 16, and a third floor 13.
The floors 14, 16, 18 are serviced by a head-end station or
head-end unit (HEU) 20, through a main distribution frame 22, to
provide a coverage area 24 in the building infrastructure 12. Only
the ceilings of the floors 14, 16, 18 are shown in FIG. 1 for
simplicity of illustration.
[0021] In an example embodiment, the HEU 20 is located within the
building infrastructure 12, while in another example embodiment the
HEU 20 may be located outside of the building infrastructure 12 at
a remote location. A base transceiver station (BTS) 25, which may
be provided by a second party such as a cellular service provider,
is connected to the HEU 20, and can be co-located or located
remotely from the HEU 20. In a typical cellular system, for
example, a plurality of base transceiver stations are deployed at a
plurality of remote locations to provide wireless telephone
coverage. Each BTS serves a corresponding cell and when a mobile
station enters the cell, the BTS communicates with the mobile
station. Each BTS can include at least one radio transceiver for
enabling communication with one or more subscriber units operating
within the associated cell.
[0022] A main cable 26 is optically coupled to or includes multiple
fiber optic cables 32 distributed throughout the building
infrastructure 12, which are coupled to remote units 28 that
provide the coverage area 24 for the first, second and third floors
14, 16, and 18. The remote units 28 may also be referred to as
"remote antenna units." Each remote unit 28 in turn services its
own coverage area in the coverage area 24. The main cable 26 can
include a riser cable 30 that carries all of the uplink and
downlink fiber optic cables 32 to and from the HEU 20. The main
cable 26 can also include one or more multi-cable (MC) connectors
adapted to connect select downlink and uplink optical fiber cables
to a number of fiber optic cables 32. In this embodiment, an
interconnect unit (ICU) 34 is provided for each floor 14, 16, 18,
the ICUs 34 including a passive fiber interconnection of optical
fiber cable ports which will be described in greater detail below.
The fiber optic cables 32 can include matching connectors. In an
example embodiment, the riser cable 30 includes a total of
thirty-six (36) downlink and thirty-six (36) uplink optical fibers,
while each of the six (6) fiber optic cables 32 carries six (6)
downlink and six (6) uplink optical fibers to service six (6)
remote units 28. Each fiber optic cable 32 is in turn connected to
a plurality of remote units 28 each having an antenna that services
a portion of the overall coverage area 24.
[0023] In this example embodiment, the HEUs 20 provide electrical
radio-frequency (RF) service signals by passing (or conditioning
and then passing) such signals from one or more outside networks 21
to the coverage area 24. The HEUs 20 are electrically coupled to an
electrical-to-optical (E/O) converter 36 within the HEU 20 that
receives electrical RF service signals from the one or more outside
networks 21 and converts them to corresponding optical signals. The
optical signals are transported over the riser cables 30 to the
ICUs 34. The ICUs 34 may include passive fiber interconnection of
optical fiber cable ports that pass the optical signals over the
fiber optic cables 32 to the remote units 28 to provide the
coverage area 24. In an example embodiment, the E/O converter 36
includes a laser suitable for delivering sufficient dynamic range
for the RoF applications, and optionally includes a laser
driver/amplifier electrically coupled to the laser. Examples of
suitable lasers for the E/O converter 36 include laser diodes,
distributed feedback (DFB) lasers, Fabry-Perot (FP) lasers, and
vertical cavity surface emitting lasers (VCSELs).
[0024] The HEUs 20 are adapted to perform or to facilitate any one
of a number of RoF applications, including but not limited to
radio-frequency identification (RFID), wireless local area network
(WLAN) communication, and/or cellular phone service. In a
particular example embodiment, this includes providing WLAN signal
distribution as specified in the IEEE 802.11 standard, i.e., in the
frequency range from 2.4 to 2.5 GHz and from 5.0 to 6.0 GHz. In
another example embodiment, the HEUs 20 provide electrical RF
service signals by generating the signals directly. In yet another
example embodiment, the HEUs 20 coordinate the delivery of the
electrical RF service signals between client devices within the
coverage area 24.
[0025] The number of optical fibers and fiber optic cables 32 can
be varied to accommodate different applications, including the
addition of second, third, or more HEUs 20. In this example, the
RoF distributed communication system 10 incorporates multiple HEUs
20 to provide various types of wireless service to the coverage
area 24. The HEUs 20 can be configured in a master/slave
arrangement where one HEU 20 is the master and the other HEU 20 is
a slave. Also, one or more than two HEUs 20 may be provided
depending on desired configurations and the number of coverage area
24 cells desired.
[0026] FIG. 2 is a schematic diagram of an example embodiment of
the HEU 20 connected to one of the remote units 28 to facilitate
further discussion of operational aspects of the RoF distributed
communication system 10 of FIG. 1 The remote unit 28 creates a
picocell 39 that together with other picocells 39 formed from other
remote units 28, as illustrated in FIG. 1, provide the coverage
area 24. The HEU 20 includes a service unit 40 that provides
electrical RF service signals for a particular wireless service or
application. In an example embodiment, the service unit 40 provides
electrical RF service signals by passing (or conditioning and then
passing) such signals from the one or more outside networks 21. The
service unit 40 is electrically coupled to an electrical-to-optical
(E/O) converter 42 that receives an electrical RF service signal
from the service unit 40 and converts it to a corresponding optical
signal. The HEU 20 also includes an optical-to-electrical (O/E)
converter 44 electrically coupled to the service unit 40. The O/E
converter 44 receives an optical RF service signal and converts it
to a corresponding electrical signal. In an example embodiment, the
O/E converter 44 is a photodetector, or a photodetector
electrically coupled to a linear amplifier. The E/O converter 42
and the O/E converter 44 constitute a "converter pair" 46.
[0027] In an example embodiment, the service unit 40 includes an RF
signal modulator/demodulator unit 48 that generates an RF carrier
of a given frequency and then modulates RF signals onto the
carrier. The RF signal modulator/demodulator unit 48 also
demodulates received RF signals. The service unit 40 also includes
a digital signal processing unit ("digital signal processor") 50, a
central processing unit (CPU) 52 for processing data and otherwise
performing logic and computing operations, and a memory unit 54 for
storing data, such as system settings and status information, RFID
tag information, etc. In an example embodiment, the different
frequencies associated with the different signal channels are
created by the RF signal modulator/demodulator unit 48 generating
different RF carrier frequencies based on instructions from the CPU
52. Also, as described below, the common frequencies associated
with a particular combined picocell are created by the RF signal
modulator/demodulator unit 48 generating the same RF carrier
frequency.
[0028] With continuing reference to FIG. 2, in an example
embodiment, the fiber optic cable 32 from the converter pair 46 in
the HEU 20 is connected to the ICU 34. The ICU 34 provides a
passive connection of the optical signals from the HEU 20 to the
remote unit 28, as will be described below. The remote unit 28 also
includes a converter pair 46, wherein the E/O converter 42 and the
O/E converter 44 therein are electrically coupled to an antenna
system 56 via an RF signal-directing element 58, such as a
circulator. Because the converter pair 46 in the remote unit 28
requires power to operate, a power distribution module 59 is also
provided in the ICU 34 to distribute power to the remote unit 28
and any other remote units 28 connected to the ICU 34. Power is
required to power the converter pair 46 and/or other
power-consuming components in the remote unit 28. According to one
aspect of the present embodiment, providing power to the remote
units 28 from the ICU 34 prevents the need for each remote unit 28
to provide a power supply thus saving cost and reducing the size of
the remote units 28. Further, the remote unit 28 may not be in
sufficient proximity to a power source to be placed such that the
picocell 39 is in the desired area. Providing power from the HEU 20
would require providing power either in separate cables or within
the riser cables 30, which would require the HEU 20 to provide
sufficient power for all possible remote units 28 adding complexity
and cost.
[0029] In this embodiment, a DC power converter 60 is electrically
coupled to the converter pair 46 in the remote unit 28, and changes
the voltage or levels of an electrical power signal generated by a
power supply 100 (FIG. 3) and provided over electrical power lines
61 to the power level(s) required by the power-consuming components
in the remote unit 28. In an example embodiment, the DC power
converter 60 is either a DC/DC power converter, or an AC/DC power
converter, depending on the type of electrical power signal carried
by the electrical power line 61. In an example embodiment, the
electrical power line 61 includes standard
electrical-power-carrying electrical wire(s), e.g., 18-26 AWG
(American Wire Gauge) used in standard telecommunications and other
applications. More detail regarding an exemplary power distribution
module 59 that can be provided in the ICU 34 is described in more
detail below starting with FIG. 3.
[0030] Turning back to FIG. 2, the RF signal-directing element 58
serves to direct the downlink and uplink electrical RF service
signals. In an example embodiment, the antenna system 56 includes
one or more patch antennas, such as disclosed in U.S. Patent
Application Publication No. 2008/0044186, published on Feb. 21,
2008, which patent application is incorporated herein by reference.
The remote unit 28 in this embodiment has few signal-conditioning
elements and no digital information processing capability. Rather,
the information processing capability is located remotely in the
HEU 20, and in a particular example, in the service unit 40. This
allows the remote unit 28 to be very compact and virtually
maintenance-free. In addition, the preferred example embodiment of
the remote unit 28 consumes very little power, is transparent to RF
signals, and does not require a local power source, as will be
described in more detail below.
[0031] With reference again to FIG. 2, the fiber optic cable 32
includes a downlink optical fiber 62D having an input end 63 and an
output end 64, and an uplink optical fiber 62U having an input end
66 and an output end 68. The downlink and uplink optical fibers 62D
and 62U optically couple the converter pair 46 in the HEU 20 to the
converter pair 46 in the remote unit 28. Specifically, the downlink
optical fiber input end 63 is optically coupled to the E/O
converter 42 of the HEU 20, while the output end 64 is optically
coupled to the O/E converter 44 of the remote unit 28. Similarly,
the uplink optical fiber input end 66 is optically coupled to E/O
converter 42 of the remote unit 28, while the output end 68 is
optically coupled to the O/E converter 44 of the HEU 20. In an
example embodiment, the RoF distributed communication system 10
employs a known telecommunications wavelength, such as 850 nm, 1300
nm, or 1550 nm as examples. In another example embodiment, the RoF
distributed communication system 10 employs other less common but
suitable wavelengths, such as 980 nm as an example.
[0032] With reference to the RoF distributed communication system
10 of FIG. 1 and FIG. 2, the service unit 40 generates an
electrical downlink RF service signal SD ("electrical signal SD")
corresponding to its particular application. In an example
embodiment, this is accomplished by the digital signal processor 50
providing the RF signal modulator/demodulator unit 48 with an
electrical signal (not shown) that is modulated onto an RF carrier
to generate a desired electrical signal SD. The electrical signal
SD is received by the E/O converter 42 in the HEU 20, which
converts this electrical signal SD into a corresponding optical
downlink RF signal SD' ("optical signal SD'"), which is then
coupled into the downlink optical fiber 62D at the input end 63.
The optical signal SD' is tailored to have a given modulation
index. The modulation power of the E/O converter 42 is controlled
(e.g., by one or more gain-control amplifiers, not shown) to vary
the transmission power from the antenna system 56. In an example
embodiment, the amount of power provided to the antenna system 56
is varied to define the size of the associated picocell 39.
[0033] The optical signal SD' travels over the downlink optical
fiber 62D to the output end 64, where it is received by the O/E
converter 44 in the remote unit 28. The O/E converter 44 converts
the optical signal SD' back into electrical signal SD, which then
travels to the RF signal-directing element 58. The RF
signal-directing element 58 then directs the electrical signal SD
to the antenna system 56. The electrical signal SD is fed to the
antenna system 56, causing it to radiate a corresponding
electromagnetic downlink RF signal SD'' ("electromagnetic signal
SD''") according to the radiation pattern of the antenna system 56
to provide the picocell 39. A client device 70, and more particular
a client device antenna 72 associated with the client device 70,
can receive the electromagnetic signal SD'' when present in the
picocell 39. The client device antenna 72 may be part of a wireless
card or a cell phone antenna, as examples. The client device
antenna 72 converts the electromagnetic signal SD'' into an
electrical signal SD in the client device 70 (signal SD is not
shown therein).
[0034] The client device 70 can generate electrical uplink RF
signals SU (not shown in the client device 70), which are converted
into electromagnetic uplink RF signals SU'' ("electromagnetic
signal SU''") by the client device antenna 72. The electrical
signal SU is directed by the RF signal-directing element 58 to the
E/O converter 42 in the remote unit 28, which converts this
electrical signal SU into a corresponding optical uplink RF signal
SU' ("optical signal SU'"), which is then coupled into the input
end 66 of the uplink optical fiber 62U. The optical signal SU'
travels over the uplink optical fiber 62U to the output end 68,
where it is received by the O/E converter 44 in the HEU 20. The O/E
converter 44 converts the optical signal SU' back into electrical
signal SU, which is then directed to the service unit 40. The
service unit 40 receives and processes the electrical signal SU,
which in an example embodiment includes one or more of the
following: storing the signal information; digitally processing or
conditioning the signals; sending the signals to one or more
outside networks 21 via network links 74; and sending the signals
to one or more client devices 70 in the coverage area 24. In an
example embodiment, the processing of electrical signal SU includes
demodulating this electrical signal in the RF signal
modulator/demodulator unit 48, and then processing the demodulated
signal in the digital signal processor 50.
[0035] FIG. 3 is a schematic diagram illustrating more detail
regarding the exemplary ICU 34 in the RoF distributed communication
system 10 of FIGS. 1 and 2. To provide the optical connections
between optical fibers in the riser cable 30 and the remote units
28, a furcation 80 from the riser cable 30 connected to the HEU 20
is brought to the ICU 34. The furcation 80 breaks pairs of optical
fibers 82 from the riser cable 30 into optical communication input
links. The optical communication input links in this embodiment are
downlink and uplink optical fibers 62D, 62U configured to be
connected to the remote units 28. The downlink optical fiber 62D
carries RoF signals from the HEU 20 to the remote units 28, and the
uplink optical fiber 62U carries RoF signals from the remote units
28 to the HEU 20. The furcation 80 contains at least two optical
fibers 82 in one or more furcated legs 84 to provide at least one
downlink and uplink optical fiber 62D, 62U pair to allow the ICU 34
to service one remote unit 28. However, more than one pair of
optical fibers 82 may be provided by the furcation 80 to allow the
ICU 34 to service more than one remote unit 28. A pair of downlink
and uplink optical fibers 62D, 62U is provided for each remote unit
28 serviced by the ICU 34. Each of the downlink and uplink optical
fibers 62D, 62U may be provided in one furcation 80 as illustrated
in FIG. 3, or in multiple furcations brought to the ICU 34.
[0036] To complete the connection of the downlink and uplink
optical fibers 62D, 62U to the remote units 28, the furcated legs
84 are connected to optical fibers in furcated legs 86. The
furcated legs 86 are provided from furcations 88 of fiber optic
cables 90 from the remote units 28 to provide optical communication
output links. In this embodiment, the ICU 34 is configured to
service up to six (6) remote units 28. The furcated legs 84 may be
pre-connectorized with a fiber optic connector 92 to facilitate
easy connections within the ICU 34. The fiber optic connectors 92
can be connected to fiber optic adapters 94 which receive fiber
optic connectors 96 from preconnectorized furcated legs 86 to
complete the optical connection between the downlink and uplink
optical fibers in the remote units 28 to the optical fibers 82 in
the riser cable 30 from the HEU 20. Other methods of connecting the
optical fibers 82 to the remote units 28, including but not limited
to splicing and the providing of splices and/or splice trays in the
ICU 34, are also possible.
[0037] As previously stated, the remote units 28 contain
power-consuming components that must be powered for the remote unit
28 to properly operate. In this regard in this exemplary
embodiment, the fiber optic cables 90 contain electrical
conductors, namely two conductors for power and ground in this
example, that allow power to be distributed through the fiber optic
cables 90 to multiple remote units 28. The fiber optic cables 90
may be hybrid cables that contain both optical fibers and
electrical conductors as shown FIG. 3, or the electrical conductors
could be run through separate wiring or cabling to the remote units
28 if desired. In this exemplary embodiment, the furcations 88
provide electrical furcated legs 98 that are configured to receive
power. The electrical furcated legs 98 are electrically coupled to
a power distribution module 59 which receives power from a power
supply 100 to provide power to the remote units 28. By providing
the power supply 100 and the power distribution module 59 in the
ICU 34, power sources do not have to be provided in the remote
units 28, nor do the remote units 28 have to be located within
reach of power sources. Further, the HEU 20 does not have to
provide power supplies and associated electrical cabling to power
the remote units 28. The power supply 100 associated with the ICU
34 can distribute power to multiple remote units 28.
[0038] In this embodiment, the power supply 100 is located within
the ICU 34, but could also be located outside of the ICU 34. The
power supply 100 may also be an uninterruptable power supply. The
power supply 100, which may be also referred to as a bulk power
supply 100, provides DC power to the remote units 28 in this
embodiment. The power supply 100 receives either AC or DC power
into a power input 102. The power input 102 may receive 110V to
240V AC or DC power from a power line 104 connected to a power
source 106 as an example. In one embodiment, a transformer (not
shown) converts AC power from the power input 102 to DC power on a
power output 108. For example, the AC/DC transformer could
transform 110V-240V alternating current (AC) power that is readily
available in the building infrastructure 12 into DC power for
distribution by the power distribution module 59 to the remote
units 28. An another example, a DC/DC converter could be provided
in the power supply 100 to convert DC power on the power input 102
to DC power on the power output 108. The power from the power
supply 100 is split to each of the remote units 28 as will be
described in more detail below.
[0039] The power supply 100 can be provided to produce any voltage
level of DC power desired. In one embodiment, the power supply 100
can produce relatively low voltage DC current to the electrical
power lines 61. Likewise, the power distribution module 59 can
support distributing the low voltage DC power provided by the power
supply 100 to the electrical conductors in the electrical power
lines 61 for powering the remote units 28. In this example, the
power output 108 is a low voltage of approximately forty-eight (48)
volts DC or less, and may be in the range of twenty-four to
forty-eight (48) Volts DC. A low voltage may be desired so that the
ICU 34 is power-limited and Safety Extra Low Voltage (SELV)
compliant, although such is not required. For example, according to
Underwriters Laboratories (UL) Publication No. 69060,
SELV-compliant circuits produce voltages that are safe to touch
both under normal operating conditions and after faults. The
voltage between any two conductors and between any one conductor
and ground (i.e., earth) should not exceed 60V DC and 42.4 Volts
peak under normal operating conditions. The total power for a SELV
compliant power supply is limited to approximately 100 VA. Article
725 of the National Electric Code (NEC) provides for power-limited
circuits. The 100 VA limit discussed therein is for a Class 2 DC
power source, as shown in Table 11(B) in Article 725. Providing a
SELV compliant power supply 100 and ICU 34 may be desired or
necessary for fire protection and to meet fire protection and other
safety regulations and/or standards. Further, since operations may
frequently interact with the ICU 34 and the connections provided
therein during installation and configurations of the ICU 34 and
the optical connections provided therein between the optical fibers
in the riser cable 30 and the remote units 28, providing a power
supply 100 that produces a SELV may be desired to avoid accidental
shocks or electrocutions.
[0040] It may further be desired to provide additional power
management features in the power distribution module 59 before the
power from the power supply 100 is transferred from the ICU 34 to
the remote units 28. For example, as illustrated in FIG. 3, the
power distribution module 59 can include one or more voltage
protection circuits 110. For example, an over-voltage protection
circuit 112 may be provided in the power distribution module 59
that is coupled to input power lines 113 from the power supply 100
to prevent power surges from damaging equipment or circuits within
the ICU 34 and at the remote units 28. The over-voltage protection
circuit 112 redirects power from the power supply 100 away from
power branches 115 in the power distribution module 59 if an
over-voltage condition is detected. By example only, the
over-voltage protection circuit 112 may be designed to redirect
power if the voltage level is greater than five to fifty percent
(5-50%) above the nominal voltage level for the power supply 100.
Providing over-voltage protection also protects against surges due
to electrostatic discharge (ESD) events which may occur due to
discharges by the power supply 100, such as due to malfunctions,
electrostatic energy present in areas surrounding the power supply
100 and/or the ICU 34, and/or from technician intervention, such as
if a technician is not properly grounded when servicing the ICU
34.
[0041] In this embodiment, as illustrated in FIG. 3, the
over-voltage protection module 112 is located in the power
distribution module 59 in a common branch 114 prior to the power
being split and distributed among power branches 115 that are
electrically coupled to the remote unit 28. The voltage level is
split to each of the power branches 115 in parallel, so voltage
levels in each of the power branches 115 is the same or essentially
the same. Thus, it is not necessary to protect each individual
power branch 115 from an over-voltage condition. An over-voltage
condition, if present, would be present in each of the power
branches 115 without distinction. However, the over-voltage
protection circuit 112 could be provided in each power branch 115
if desired, but such would likely incur additional costs. More
discussion regarding an exemplary embodiment of the over-voltage
protection circuit 112 is described below with regard to FIG.
4.
[0042] It may also further be desired to provide reverse-voltage
protection in the power distribution module 59 to protect against a
reverse-voltage condition. Reverse-voltage protection prevents a
reverse polarity (i.e., a negative voltage) in voltage from being
supplied by the power supply 100, which could otherwise damage
components in the power distribution module 59 and at the remote
units 28. For example, a technician may accidentally reverse power
and ground lines or leads in the input power lines 113 leading from
the power supply 100 to the power distribution module 59. Certain
components in the power distribution module 59 and/or the remote
unit 28 may be damaged if a reverse-voltage is applied to certain
of their components. In this regard, a reverse-voltage protection
circuit 116 may be provided in the power distribution module 59
that is coupled to the input power lines 113 from the power supply
100. The reverse-voltage protection circuit 116 redirects power
from the power supply 100 away from the power branches 115 if a
reverse voltage condition is detected. For example, the
reverse-voltage protection circuit 116 may redirect power if the
voltage level produced by the power supply 100 reaches 0.3 to 5.0
V.
[0043] In this embodiment, as illustrated in FIG. 3, the
reverse-voltage protection module 116 is located in the power
distribution module 59 in the common branch 114 prior to the power
being split and distributed among power branches 115 that are
electrically coupled to the remote unit 28. A reverse-voltage
condition, if present, would be present in each of the power
branches 115 without distinction. However, the reverse-voltage
protection circuit 116 could be provided in each power branch 115
if desired. More discussion regarding an exemplary embodiment of
the reverse-voltage protection circuit 116 is described below with
regard to FIG. 4.
[0044] Within each power branch 115, current protection and other
power detection and related circuits may be provided. In the
embodiment in FIG. 3, the power supply 100 is power enough to
supply power to all remote units 28 connected to the ICU 34. Thus,
the power supply 100 is powerful enough to produce an over-current
condition in a power branch 115 if a power splitting malfunction
occurs. In this regard and in this embodiment as illustrated in
FIG. 3, over-current protection circuits 118 may be provided in
each power branch 115. In this embodiment, the ICU 34 is configured
to support up to six (6) remote units 28, and thus six (6)
over-current protection circuits 118 are provided, although such is
not required or limiting. The over-current protection circuits 118
are electrically coupled to split power outputs 120 from the
voltage protection circuit(s) 110 in this embodiment. The
over-current protection circuits 118 protect the components in the
ICU 34 and the remote units 28 from being damaged due to an
over-current condition generated by the power supply 100 or other
cause, such as an unintended short circuit in the power
distribution module 59 for example.
[0045] Unlike the voltage protection circuits 110, the over-current
protection circuits 118 are included in the individual power
branches 115 since current level can differ among the power
branches 115. By placing the over-current protection circuits 118
in each power branch 114, over-current conditions present in a
particular power branch 115 can be isolated. However, the
over-current protection circuit 118 could be placed in a common
branch 114 if desired. As an example, the over-current protection
circuits 118 may be designed to detect if the current level is at
least approximately five to two hundred percent (5-200%) above
nominal current levels in a power branch 115. More discussion
regarding an exemplary embodiment of the over-current protection
circuits 118 is described below with regard to FIGS. 4 and 5.
[0046] It may also be desired to provide an under-voltage sensing
circuit 122 in the power distribution module 59. An under-voltage
level (but not meaning reverse voltage) typically will not damage
components in the ICU 34 and the remote units 28. However,
under-voltage conditions can cause the ICU 34 and/or the remote
units 28 to not properly operate. Some circuits and components,
including those that may be provided in the power branches 115 of
the ICU 34 and in the remote units 28, require a minimum operation
voltage to properly operate. If the voltage level produced by the
power supply 100 is insufficient, a remote unit 28 may not properly
operate and may go offline, meaning that the remote unit 28 may not
send and receive RF signals to a client device 70 (see FIG. 2).
Thus, sensing under-voltage conditions can assist in
troubleshooting the ICU 34 and the power supply 100 and/or power
distribution module 59.
[0047] The under-voltage sensing circuits 122 are electrically
coupled to outputs 123 of the under-current protection circuits 118
in this embodiment, as illustrated in FIG. 3. The under-voltage
sensing circuits 122 are located on the remote unit 28 side of the
power distribution module 59 so that any over-voltage,
reverse-voltage, and/or over-current protections are provided
before the power reaches the under-voltage sensing circuits 122 in
this embodiment. The under-voltage sensing circuits 122 require
power from the power supply 100 to operate in this embodiment.
Further, it may be desired to detect the power levels in each of
the power branches 115 individually. Thus, since the ICU 34 is
configured to support up to six (6) remote units 28 in this
embodiment, six (6) under-voltage power sensing circuits 122 are
provided, although such is not required or limiting.
[0048] If a remote unit 28 is not properly operating, a technician
may be dispatched to diagnose the problem. If the problem is a
result of an insufficient or under-voltage provided by the power
supply 100, the under-voltage sensing circuit 122 can indicate to
the technician that an insufficient voltage level is being produced
by the power supply 100. The power distribution module 59 may
include power level indicators 124 that are electrically coupled to
each under-voltage sensing circuit 122 to provide an indication of
the power level in the power distribution module 59 to a technician
or other device. As an example, the power level indicators 124 may
have a visual indicator, such as one or more light emitting diodes
(LEDs) as an example, indicative of the voltage level or an
under-voltage condition in the ICU 34. If the power level is
insufficient as a result of any power level condition, including an
under-voltage condition, corrective measures can be taken, such as
diagnosing the power connections in the ICU 34 as an example, and
replacing the power supply 100, if needed. More discussion
regarding an exemplary embodiment of the under-voltage sensing
circuits 122 is described below with regard to FIGS. 4 and 5.
[0049] Unless the over-voltage protection circuit 112, the
reverse-voltage protection circuit 116, and/or the over-current
protection circuits 118 redirect power, the power distribution
module 59 transfers the received power from the power supply 100 to
the power output lines 126. To couple the power to the remote units
28 in this embodiment, the power output lines 126 are electrically
coupled to the electrical furcated legs 98, which are run to each
of the remote units 28. The power output lines 126 may be separate
power lines that are electrically connected to the electrical
furcated legs 98, or the electrical furcated legs 98 for each of
the remote units 28 may be directly connected to over-voltage
protection circuits 112.
[0050] FIG. 4 illustrates a schematic diagram of the power
distribution module 59 in FIG. 3 illustrating more details
regarding the circuit and the components contained therein for this
embodiment. As illustrated in FIG. 4, the input power lines 113
come from the power supply 100 into the power distribution module
59. The positive input power line 113 is coupled to a V.sub.S1 node
130 and a ground (GND) node 132. The voltage protection circuit 110
is provided in this embodiment by the V.sub.S1 node 130 being
coupled to a cathode k of a diode 134 configured in a reverse bias
mode. The anode `a` of the diode 134 is coupled to the GND node
132. A fuse 136 is also coupled to the cathode `k` of the diode 134
in this embodiment. During normal voltage levels, the diode 134 is
an open circuit. Current flows through the fuse 136 and the voltage
level is applied in parallel on each of the power outputs 120 to
each of the power branches 115 as illustrated in FIG. 3.
[0051] When the voltage level supplied from the power supply 100 at
the V.sub.S1 node 130 rises above an excess voltage level
approximately equal to the activation voltage drop level in order
to activate or "turn-on" the diode 134, the diode 134 will become a
short circuit to shunt excess current to the GND node 132. This
directs power from the power supply 100 away from the remainder of
the components in the power branches 115 of the power distribution
module 59 (as illustrated in FIG. 3) and protects the remote units
28 from an over-voltage condition. Also, the fuse 136 becomes an
open circuit in response to the over-current draw from the power
supply 100 as a result of the short circuit operation of the diode
134 to provide a current limiting function to protect the diode
134. Further, because the diode 134 is provided in a reverse bias
mode, the diode 134 will also short to the GND node 124 when a
negative voltage is applied across the V.sub.S1 and GND nodes 130,
132. Thus, in this example, the over-voltage protection circuit 112
and the reverse-voltage protection circuit 116 are provided as part
of the same circuit, although such is not required.
[0052] In this embodiment, the diode 134 is a transient voltage
suppression (TVS) diode. A TVS diode can be used to protect
sensitive electronics from voltage spikes. A TVS diode is similar
to a Zener diode in that it permits current in the forward
direction like a normal diode, but also in the reverse direction if
the voltage is larger than a breakdown voltage. Thus, a TVS diode
can be used to protect for both over-voltage and reverse-voltage
conditions. However, any type of over-voltage protection device may
be employed. In this embodiment, the fuse 136 is a power
temperature coefficient (PTC) fuse which is resettable to provide a
short circuit for normal operation when the current drawn from the
power supply 100 lowers beyond the current limiting threshold of
the PTC fuse. However, any type of over-current protection device
may be employed. A resettable fuse may be desirable to prevent the
fuse from having to be manually replaced.
[0053] Further, in this embodiment, a second diode 134' and
resettable fuse 136' are provided in parallel and coupled to the
V.sub.S1 node 130 and the GND node 132. The second diode 134' and
resettable fuse 136' partition the over-voltage and reverse-voltage
protection between the two diodes 134, 134' and the current
limiting over the two fuses 136, 136' to narrow the required
current voltage and current limiting range of the diodes 134, 134'
and the fuses 136, 136', respectively. However, only one partition
or more than two partitions may be provided as desired.
[0054] The power distribution module 59 in this embodiment also
includes a DC-to-DC converter 140 to provide a second voltage at
V.sub.S2 node 142 from the voltage provided by the power supply 100
at the V.sub.S1 node 130. In this example, the voltage level
provided by the power supply 100 at the V.sub.S1 node 130 is
approximately 48V. The DC-to-DC converter 140 is configured to
transform this 48V to approximately 5V at the V.sub.S2 node 142.
This is so a lower voltage can be used to provide power to the
under-voltage sensing circuits 122 and power level indicators 124
in the power distribution module 59 that require approximately 5V
in this example.
[0055] FIG. 5 illustrates an over-current protection circuit 118
and under-voltage sensing circuit 122 in one power branch 115 of
the power distribution module 59 of FIG. 3. It is understood that
the illustrated over-current protection circuit 118 and
under-voltage sensing circuit 122 in FIG. 5 may be provided in each
of the power branches 115 in the power distribution module 59, but
for simplicity of illustration and discussion purposes, only one
over-current protection circuit 118 and under-voltage sensing
circuit 122 for one power branch 115 is illustrated in FIG. 5. The
discussion here is equally applicable for all other power branches
115 of the power distribution module 59.
[0056] As illustrated in FIG. 5, the over-current protection
circuit 118 is provided in the form of a fuse 144 in this
embodiment. The fuse 144 provides an open circuit if the current
exceeds a designed current level according to the type and
characteristics of the fuse 144. In this embodiment, the fuse 144
is a PTC resettable fuse. The fuse 144 resets when the current
level lowers beyond the over-current condition. During normal
current conditions or once the fuse 144 resets after an
over-current condition, the current flows to an output node 146 of
the fuse 144, which is coupled to the power output lines 126
electrically coupled to the remote units 28 to provide power to the
remote units 28. To output node 146 of the fuse 144 is also coupled
in parallel to the under-voltage sensing circuit 122 and power
level indicator 124 in this embodiment, as illustrated in FIG. 5.
The under-voltage sensing circuit 122 monitors the voltage level
and does not redirect power.
[0057] The output node 146 is coupled to a resistor divider network
148 to provide a ratio of the voltage level to a node 150 that is
input into an input voltage pin (VIN) in a voltage comparator 152.
In this embodiment, the voltage comparator 152 is an integrated
circuit (IC) provided in an IC chip. For example, the voltage
comparator 152 may be the MC33064 under-voltage sensing integrated
circuit IC. The reference voltage is set in an internal circuit in
the voltage comparator 152 in this embodiment. However, any type of
voltage comparator 152 may be provided. If the voltage level on the
node 150 drops below a reference voltage level setting in the
voltage comparator 150, the voltage comparator 152 pulls a reset
line 154 to a low or zero voltage. The reset line 154 is coupled to
an input 156 of a switch 158, which may be a transistor, including
but not limited to a field effect transistor (FET), or any other
type of transistor. A pull-up resistor 160 is coupled between the
V.sub.S2 node 142 and the reset line 154 to provide a bias voltage
to the switch 158. If the switch 158 is activated by the reset line
154 being pulled low, the switch 158 activates or turns on to
provide a current flow path between the V.sub.S2 node 142 and the
GND node 132. Current flows through an LED 161 to emit light to
indicate the under-voltage condition to a technician. A
current-limiting resistor 162 protects the LED 161 from an
over-current condition.
[0058] Depending on the environmental conditions, the power supply
100 associated with the ICU 34 may behave differently at reduced
conditions. For example, at higher temperatures, the output wattage
of the power supply 100 described above and illustrated in FIG. 3
can be reduced from approximately 180 W (e.g., at room temperature)
to 140 W (i.e., at higher temperatures) under maximum loads. This
reduction in power may not be sufficient to properly power the
remote units 28 depending on the number of remote units 28
connected to the ICU 34. For example, in the ICU 34 example in FIG.
3, the remote units 28 may require approximately 36-40 W of power
for a total of between 144 W-150 W. However, at elevated
temperatures, the power supply 100 may be unable to provide this
power to each power branch 115 in the power distribution module 59.
Selecting a power supply 100 with a higher power rating to
compensate for reduction in power due to reduced conditions may not
be possible in order to comply with low voltage requirements
previously described. Additional cooling devices, such as fans or
heat sinks, may also be required, adding cost to the ICU 34.
[0059] In this regard, FIG. 6 illustrates an alternate embodiment
of the ICU 34 that may be employed to provide sufficient power to
the remote units 28 under reduced conditions. In this embodiment,
more than one power supply 100 is provided. Power from each power
supply 100 can be partitioned to only provide power to a subset of
the remote units 28. Each power supply 100 provides power to its
own dedicated power distribution module 59 which in turn services a
subset of the maximum remote units 28 that can be connected to the
ICU 34. Providing multiple power supplies 100 also reduce the power
output requirements of each power supply 100 over the requirements
should a single power supply 100 be employed like provided in the
exemplary ICU 34 of FIG. 3. Note that providing more than one power
supply 100 is not required. For example, the maximum number of
remote units 28 could be reduced to compensate for reduced
conditions of the power supply 100 as an alternative. Further, the
power requirements of the remote units 28 could be reduced to lower
the overall power requirements on the power supply 100 as another
alternative.
[0060] FIG. 7 illustrates an exemplary ICU 34 that may be employed
in the exemplary Radio-over-Fiber (RoF) distributed communication
system 10 of FIGS. 1 and 2 and may be configured according to any
of the embodiments described above. As illustrated in FIG. 7, the
ICU 34 may be provided in an enclosure 170. The enclosure 170 may
have side doors 172, 174 that are configured to hold the furcations
88, 80, respectively from the fiber optic cable 90 to the remote
unit 28 and the riser cable 30, respectively (see also, FIG. 3).
The furcation 80 of the riser cable 30 breaks pairs of optical
fibers from the riser cable 30 to provide optical communication
input links. The optical communication input links in this
embodiment are the downlink and uplink optical fibers 62D, 62U
(FIG. 3) to be connected to the remote units 28. In this
embodiment, the furcated leg 86 contain twelve (12) optical fibers
to provide connections up to six (6) remote units 28 although only
one remote unit 28 is illustrated as connected in FIG. 7.
[0061] To complete the passive connection of the downlink and
uplink optical fibers 62D, 62U to the remote units 28, the furcated
legs 84 are connected to furcated legs 86 provided in furcations 88
of fiber optic cables 90 from the remote units 28. The furcated
legs 84 are pre-connectorized with the fiber optic connector 92 to
facilitate easy connections within the ICU 34. The fiber optic
connectors 92 can be connected to the fiber optic adapters 94 which
receive the fiber optic connectors 96 from pre-connectorized
furcated legs 86 to complete the optical connection between the
downlink and uplink optical fibers 62D, 62U in the remote units 28
to the optical fibers 82 in the riser cable 30 from the HEU 20.
[0062] The furcations 88 also provide the electrical furcated legs
98 that are configured to receive power from the power supply 100.
The electrical furcated legs 98 are electrically coupled to a power
terminal 176 contained inside the enclosure of the ICU 34 in this
embodiment. The electrical furcated legs 98 may be
pre-connectorized with an electrical connector 178 that is
configured to connect to an electrical connector 180 in the power
terminal 176. A connection (not shown) is made between the power
terminal 176 and the power distribution module 59 which receives
power from a power supply 100 to provide power to the remote units
28. The power distribution module 59 is not shown in FIG. 7. The
power distribution module 59 may be disposed in the enclosure 170
or anywhere else desired on the ICU 34 including but not limited to
within a rear wall 182 of the enclosure 170 or on the backside of
the rear wall 182 as examples. Further in this embodiment, two
power terminals 176 are provided to support all necessary power
connections and in the event that more than one power supply 100 is
provided to partition power as illustrated and discussed by example
in FIG. 6.
[0063] The ICU discussed herein can encompass any type of fiber
optic equipment and any type of optical connections and receive any
number of fiber optic cables or single or multi-fiber cables or
connections. The ICU may include fiber optic components such as
adapters or connectors to facilitate optical connections. These
components can include, but are not limited to the fiber optic
component types of LC, SC, ST, LCAPC, SCAPC, MTRJ, and FC. The ICU
may be configured to connect to any number of remote units. One or
more power supplies either contained with the ICU or associated
with the ICU may provide power to the power distribution module in
the ICU. The power distribution module can be configured to
distribute power to remote units with or without voltage and
current protections and/or sensing. The power distribution module
contained in the ICU may be modular where it can be removed and
services or permanently installed in the ICU.
[0064] Further, as used herein, it is intended that terms "fiber
optic cables" and/or "optical fibers" include all types of single
mode and multi-mode light waveguides, including one or more bare
optical fibers, loose-tube optical fibers, tight-buffered optical
fibers, ribbonized optical fibers, bend-insensitive optical fibers,
or any other expedient of a medium for transmitting light signals.
Many modifications and other embodiments set forth herein will come
to mind to one skilled in the art to which the embodiments pertain
having the benefit of the teachings presented in the foregoing
descriptions and the associated drawings. Therefore, it is to be
understood that the description and claims are not to be limited to
the specific embodiments disclosed and that modifications and other
embodiments are intended to be included within the scope of the
appended claims. It is intended that the embodiments cover the
modifications and variations of the embodiments provided they come
within the scope of the appended claims and their equivalents.
Although specific terms are employed herein, they are used in a
generic and descriptive sense only and not for purposes of
limitation.
* * * * *